The objcg is not cleared and put for kfence object when it is freed, which could lead to memory leak for struct obj_cgroup and wrong statistics of NR_SLAB_RECLAIMABLE_B or NR_SLAB_UNRECLAIMABLE_B. Since the last freed object's objcg is not cleared, mem_cgroup_from_obj() could return the wrong memcg when this kfence object, which is not charged to any objcgs, is reallocated to other users. A real word issue [1] is caused by this bug. [1] https://groups.google.com/g/syzkaller-bugs/c/BBQFy2QraoY/m/HtBd5gbyAQAJ Reported-by: syzbot+f8c45ccc7d5d45fc5965@xxxxxxxxxxxxxxxxxxxxxxxxx Fixes: d3fb45f370d9 ("mm, kfence: insert KFENCE hooks for SLAB") Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx> --- mm/slab.c | 1 + 1 file changed, 1 insertion(+) diff --git a/mm/slab.c b/mm/slab.c index d9dec7a8fd79..b04e40078bdf 100644 --- a/mm/slab.c +++ b/mm/slab.c @@ -3422,6 +3422,7 @@ static __always_inline void __cache_free(struct kmem_cache *cachep, void *objp, if (is_kfence_address(objp)) { kmemleak_free_recursive(objp, cachep->flags); + memcg_slab_free_hook(cachep, &objp, 1); __kfence_free(objp); return; } -- 2.11.0
